github.com/murrekatt/go-ethereum@v1.5.8-0.20170123175102-fc52f2c007fb/core/evm.go (about)

     1  // Copyright 2014 The go-ethereum Authors
     2  // This file is part of the go-ethereum library.
     3  //
     4  // The go-ethereum library is free software: you can redistribute it and/or modify
     5  // it under the terms of the GNU Lesser General Public License as published by
     6  // the Free Software Foundation, either version 3 of the License, or
     7  // (at your option) any later version.
     8  //
     9  // The go-ethereum library is distributed in the hope that it will be useful,
    10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
    11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
    12  // GNU Lesser General Public License for more details.
    13  //
    14  // You should have received a copy of the GNU Lesser General Public License
    15  // along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
    16  
    17  package core
    18  
    19  import (
    20  	"math/big"
    21  
    22  	"github.com/ethereum/go-ethereum/common"
    23  	"github.com/ethereum/go-ethereum/core/types"
    24  	"github.com/ethereum/go-ethereum/core/vm"
    25  )
    26  
    27  // BlockFetcher retrieves headers by their hash
    28  type HeaderFetcher interface {
    29  	// GetHeader returns the hash corresponding to their hash
    30  	GetHeader(common.Hash, uint64) *types.Header
    31  }
    32  
    33  // NewEVMContext creates a new context for use in the EVM.
    34  func NewEVMContext(msg Message, header *types.Header, chain HeaderFetcher) vm.Context {
    35  	return vm.Context{
    36  		CanTransfer: CanTransfer,
    37  		Transfer:    Transfer,
    38  		GetHash:     GetHashFn(header, chain),
    39  
    40  		Origin:      msg.From(),
    41  		Coinbase:    header.Coinbase,
    42  		BlockNumber: new(big.Int).Set(header.Number),
    43  		Time:        new(big.Int).Set(header.Time),
    44  		Difficulty:  new(big.Int).Set(header.Difficulty),
    45  		GasLimit:    new(big.Int).Set(header.GasLimit),
    46  		GasPrice:    new(big.Int).Set(msg.GasPrice()),
    47  	}
    48  }
    49  
    50  // GetHashFn returns a GetHashFunc which retrieves header hashes by number
    51  func GetHashFn(ref *types.Header, chain HeaderFetcher) func(n uint64) common.Hash {
    52  	return func(n uint64) common.Hash {
    53  		for header := chain.GetHeader(ref.ParentHash, ref.Number.Uint64()-1); header != nil; header = chain.GetHeader(header.ParentHash, header.Number.Uint64()-1) {
    54  			if header.Number.Uint64() == n {
    55  				return header.Hash()
    56  			}
    57  		}
    58  
    59  		return common.Hash{}
    60  	}
    61  }
    62  
    63  // CanTransfer checks wether there are enough funds in the address' account to make a transfer.
    64  // This does not take the necessary gas in to account to make the transfer valid.
    65  func CanTransfer(db vm.StateDB, addr common.Address, amount *big.Int) bool {
    66  	return db.GetBalance(addr).Cmp(amount) >= 0
    67  }
    68  
    69  // Transfer subtracts amount from sender and adds amount to recipient using the given Db
    70  func Transfer(db vm.StateDB, sender, recipient common.Address, amount *big.Int) {
    71  	db.SubBalance(sender, amount)
    72  	db.AddBalance(recipient, amount)
    73  }